P0117
Medium SeverityEngine Coolant Temperature Sensor Circuit Low
Cooling System
What Does P0117 Mean?
ECT sensor voltage is too low, indicating an impossibly high temperature. Usually a shorted sensor.
Common Fix
Replace ECT sensor
Estimated Cost (DIY)
$10 - $25
Symptoms
- ⚠️Fans running at max speed constantly
- ⚠️Rich fuel mixture
- ⚠️Check engine light
- ⚠️Temp gauge pegged high
Common Causes
Shorted ECT sensorlikely
Short in sensor wiringpossible
Corroded connector pinspossible
How to Diagnose P0117
- 1Disconnect sensor — fans should stop, gauge should change
- 2Measure sensor resistance
- 3Check wiring for shorts to ground
- 4Replace sensor
Need to read or clear this code?
Shop OBD2 Scanners on Amazon →Frequently Asked Questions
- Why are my fans always on with P0117?
- The shorted sensor tells the ECM the engine is overheating, so it runs the fans at max. The engine is likely at normal temperature.
- Can P0117 cause overheating?
- No — it makes the ECM think the engine is hot, but actual temperature is fine. However, always verify with an IR thermometer.